What's going on is that your sample size is far, far too small and focused.
Your friends are your peer group. They tend to be the same age range, race, national origin, religion, and hometown area as you, or share at least one of those basic demographic data points. If you are college-educated, then a lot of them are, too.
Facebook also skews heavily college educated. Maybe look at some real stats some time, put together by a company that knows what it's doing. Pew Research puts together social media platform demographics, and they noted that in 2014, 74% of all Facebook users had at least some college under their belts. See - http://www.pewinternet.org/2015/01/09/demographics-of-key-social-networking-platforms-2/
Per that same study, of the platforms they reviewed, the lowest % of people with some college was on Instagram, with 22%.
What you had is what's called sample bias